Fibroblastic rheumatism: clinical, histological, immunohistological, ultrastructural and biochemical study of a case.

We report a case of fibroblastic rheumatism (FR). Only eight other cases of this recently described entity have been reported previously. FR is characterized by polyarthralgia and joint stiffness without joint destruction, associated with cutaneous nodules and sclerodactyly. Histology shows an increase in the number of fibroblasts and marked dermal fibrosis. Rheumatological and skin manifestations may improve with corticosteroid therapy. In our patient, immunohistochemical studies of involved and uninvolved skin showed an increase in fibronectin and tenascin deposition. In the dermis, the hyperplastic cells had phenotypic features of muscle, suggesting myofibroblastic differentiation. Ultrastructural study showed an increase in active fibroblastic cells with features of myofibroblasts. A hyperproliferative capacity was observed in fibroblasts cultured from involved skin. Biochemical studies of the production of collagen and non-collagen proteins were performed on these cultured cells, and showed a reduction in collagen and non-collagen protein synthesis by FR fibroblasts. Thus, FR appears to differ from other fibrotic skin diseases such as scleroderma, in that dermal fibrosis may be due predominantly to fibroblast proliferation with myofibroblastic differentiation without any increase in collagen synthesis.